Usually you order a cabinet in the size that matches the installation specs of a specific DW or appliance, so there shouldn't be a need for a "filler gasket".

@jaxo - I have a Miele DW (8+ years old) installed in an island that is curved so my dw opening is somewhat trapezoid in shape. Cabinets are totally custom build. When my DW was installed I thought it sounded louder that expected. I ended up putting (stuffing actually) weather stripping in between the side gaskets of the dw and the side of the cabinet. Problem was solved. DW is very quiet and can hardly tell it is running. It is rated at 44 DB.

This other discussion mentioned filler gaskets.

Gaps between cabinet and dishwasher. Mounting question (houzz.com)

They said:

" European brands are slightly less than 24" but typically are installed in a 24" space (filler gaskets are usually included to block sound transmission) to allow for a future change to a different brand. "

The Miele G 7166 SCVi XXL (for example) did well in CR's tests though not well enough to earn a "recommended" rating. At 23-5/8" wide -- only 1/4" narrower than American dishwasher such as the 23-7/8"-wide Maytag MDB4949SKZ -- it's still a tight fit in a 24" cabinet. The dishwasher does include an insulating strip to be installed between the door and toe kick as shown on page 108 of the operating instructions.

What about the quietest KitchenAid dishwashers? Aren’t those full US cabinet sized for a snug fit without spacers and gaskets?

You don't need a filler. Miele now produces full 24" dishwashers for the US market. We replaced our Whirlpool with a Miele about a year ago. The Miele fills the spot completely.

I have a newer G7106 and there still seems to be too much air space on the sides.

The G 7106 SCU XXL is also 23-5/8". If that a 3/16" gap on each side isn't satisfactory, buy something else. But Bosch dishwashers are even narrower: 23-9/16".

I had a Bosch 800 series before that was slightly less noisy, but not super quiet in this location. I was expecting this Miele to be quieter, but some parts of the cycles are actually noticeably louder. I think the drain motor hum is the biggest source of noise.

This dishwasher was a huge waste of money because I already want to replace it if there is no installation fix to quiet it down.

I may need a sub 40 dBA model to be satisfied if this just the way it is.

To work around the noise, I try running delayed cycles during the middle of the night so I don’t need to hear it, but I shouldn’t need to do that with a dishwasher rated as 43 dBA.

You have another post where you are completely redoing a kitchen? Is this the same kitchen?

Yes, but it may not be completely redoing with new lower cabinets. It’s possible that the existing cabinets will just be refaced and the issue with the dishwasher will remain.

"I was expecting this Miele to be quieter"

No CR-tested Miele dishwasher was quieter than the quietest Bosch dishwasher. You may have unrealistic expectations as the Bosch SHP78CM5N 800-series dishwasher received a 5/5 rating in noise. The SHP9PCM5N also received a 5/5 rating; its DB rating is lower but it's much more expensive.